Stratigraphy: Jurassic volcanic rocks with an age of approximately 164.5 ± 0.2 million years before present.

Distribution: The Yim Tin Tsai Formation is exposed mainly in the vicinity of Tolo Harbour, but isolated outcrops occur in the western New Territories, and on Lantau Island.

Lithology: The Yim Tin Tsai Formation is composed predominantly of lapilli-ash and lapilli-bearing coarse ash crystal tuff.

(Coarse ash crystal tuff of the Yim Tin Tsai Formation, Yim Tin Tsai, northeastern New Territories)